Hard disk drives include one or more rigid disks, which are coated with a magnetic recording medium in which data can be stored. Hard disk drives further include read and write heads for interacting with the data in the magnetic recording medium. The write head includes an inductive element for generating a magnetic field that aligns the magnetic moments of domains in the magnetic recording medium to represent bits of data.
Magnetic recording techniques include both longitudinal and perpendicular recording. Perpendicular magnetic recording (“PMR”) is a form of magnetic recording in which the magnetic moments representing bits of data are oriented perpendicularly to the surface of the magnetic recording medium, as opposed to longitudinally along a track thereof. PMR enjoys a number of advantages over longitudinal recording, such as significantly higher areal density recording capability.
Write poles with a trapezoidal cross-sectional shape at the air bearing surface (“ABS”) are used to provide improved writing performance in PMR heads. The manufacture of write poles with this trapezoidal cross-sectional shape presents a number of difficulties, however. One approach to manufacturing such poles involves a reductive process of milling poles from a layer of magnetic material. Due to the complex three-dimensional shapes called for in next-generation hard disk drives, however, this process can be extraordinarily difficult and prone to low yields. Another approach to manufacturing these poles involves an additive process, in which damascene trenches are formed in an insulating substrate layer and filled with a magnetic material.
One such approach to forming a write pole is illustrated in FIGS. 1A-1I. As can be seen with reference to FIG. 1A, a patterned mask 103 of tantalum (Ta) is provided over a substrate 102 of alumina (Al2O3) disposed on a lower substrate 101 of chromium (Cr). Patterned mask 103 has an opening 104 over a region of substrate 102 where a damascene trench will be formed. By subjecting the structure of FIG. 1A to a reactive ion etching (RIE) operation, a damascene trench 105 is formed in substrate 102, as is illustrated in FIG. 1B. To control the final shape and track width of the pole, one or more layers of alumina, such as layer 106, may be disposed via atomic layer deposition (ALD) over the structure of FIG. 1B to provide a narrower damascene trench 107, as is illustrated in FIG. 1C.
Turning to FIG. 1D, a layer of photoresist 108 is applied over the structure of FIG. 1C to open an area 109 over damascene trench 107. A high moment magnetic material 110, such as CoNiFe or the like, is then plated to fill the trench pattern formed by the foregoing photoresist process, as is illustrated in FIG. 1E. The photoresist is then stripped from the structure to create an open area on the field surrounding magnetic material 110, and a stop layer 111, such as diamond-like carbon (DLC), is deposited over the field area, as is illustrated in FIG. 1F. The stop layer allows a chemical mechanical polishing (CMP) operation to be used to remove excess magnetic material extending above the desired trailing edge of the write pole, as will be illustrated in greater detail below.
To facilitate the CMP process, another layer 112 of Al2O3 is provided over the structure of FIG. 1F, as is illustrated in FIG. 1G. The structure is subjected to the CMP process to planarize the surface on the top of stop layer 111, as is illustrated in FIG. 1H. The thickness and track width of write pole 113 are well preserved by stopping the CMP process within the thickness of stop layer 111, but where the stop layer has a gap 114 surrounding write pole 113, however, dishing in the trailing edge of write pole 113 may occur. In a final step, the remaining material from stop layer 111 is removed by another RIE process, as is illustrated in FIG. 1I.
While the foregoing process is capable of providing write poles with tightly controlled track widths and side wall angles, the use of photoresist to define a frame for plating the magnetic material may leave undesirable photoresist residue within the damascene trench and along the side walls of the write poles thus formed. Any photoresist residue can result in poor pole integrity and finishing, and may even result in device failure.